Re: Metal number on old trim.
Numbered tacks on window sills were for putting the right shutters back after taking them down to paint. This was also done with roman numerals cut into the frames/shutters with a chisel.
The shutters (now long gone, perhaps) would have the corresponding number tack driven in to them. If a subsequent painter didn't see the roman numerals, or the previous tacks, he'd add a new set. I have seen two sets on the same sills, but never three.
Remove not the ancient landmark, which your fathers have set.